Being a Rehabilitation Psychologist, i have been working in the field of Disabilit and Rehabilitation for last 2 years. I came across many misconceptions regarding disability and it was more of a concern to me when i hear such things from literate peoples. First of all i want to make clear that disability is not what others think. There are 3 terms which are used interchangeably viz. Impairment, Disability and Handicap, but these have different meanings. Impairment is when someone losses or has abnormality in his bodily structure, psychological functioning and physiology. For example we can say ‘loss of limb' or loss of certain chemicals in the brain leading to parkinson disease.

So another thing we have to consider here is that not all impairment can cause disability.

For eg. If someone has lost an earlobe (outer ear) then it would not lead to hearing loss but just a cosmetic deficiency. It will be called as an impairment but it can not lead to disability.

 Disability is the inability to do tasks because of the Impairment. It limits our ability performing a task in the manner considered normal for a human being. This can lead to participation restrictions and also prevent in obtaining health care services. 

Disability can be caused due to conditions present at birth and can affect the person in later part of the life. Conditions can include cognition (memory,learning), mobility (movement related), visual(vision) , auditory(sound), behavior related (disorders).

Now the third term is Handicap which is termed as the disadvantage the individual is facing socially resulting from impairment or a disability which will prevent him/her to perform role. For example a person who has visual impairment cannot read a book due to unavailability of braille language. A person only becomes handicap when resources are not available around him/her. A person on wheelchair wants to go for an interview but the office is at 2nd floor and their is no ramp or elevator to reach to the 2nd floor then in that case he will be called as handicap. Socioeconomic factors play an important role in determining the handicap such as skills achieved and financial condition of the family. Government of India runs different programs and schemes for the pwd's (persons with disability) based on the percentage of disability they have. It is calculated on the basis of assessments and tests.

(Note: color blindness is an impairment but not a disability but it can be handicap depending on circumstances like when a train engine driver prevented from following his occupation

I hope i am able to give an idea about the concept of disability and related terms.